1. Technical Field of the Invention
The present invention relates to a vehicle control device, and in particular, to a vehicle control device that controls a motional state of a controlled object which moves or deforms, in accordance with a manipulated variable.
2. Related Art
In a vehicle, generally, there are many portions that cause coupled vibration between at least two components coupled with each other via suspension components having an anti-vibration function based on spring-damping characteristics. As is known in related art, an example of coupled vibration is caused between (i) a vehicle body (sprung portion) coupled by suspension components, (ii) a vehicle body coupled by components of an unsprung system or engine mounts, and (iii) an engine transaxle. This coupled vibration affects ride quality of the vehicle but also travelling performance thereof.
In related art, various devices or inventions have been proposed in order to suppress the coupled vibration as explained above. For example, there is proposed a control method that controls (i) force that causes coupled vibration in an intended system, (ii) drive torque which is source of generation of torque reaction force, or (iii) another manipulated force itself, so that the coupled vibration is not produced or is rapidly damped (for example, see JP-A-2011-089474).
In JP-A-2011-089474, there is proposed a method of controlling engine torque based on an estimated value of vibration that is estimated using a model relating to roll vibration of the engine so as to suppress vibration of the engine. Specifically, in this method, the engine torque is controlled on the basis of a running condition of the vehicle, and then, a roll angle and roll angular velocity of the engine are controlled to be an amount appropriate for stabilizing the vehicle. Here, the roll angle and roll angular velocity are calculated on the basis of a steering angle and an estimated value of a lateral G-force (gravity).
However, depending on modeling of a system which is a controlled object, i.e., a mode of a mathematical description method, the known method as explained above has no design freedom and cannot express important characteristics of an actual system which is simulated. As a result, there is an issue that suitable vehicle performance cannot be exploited.
JP-A-2011-089474 discloses a method of mathematical description for spring and damping properties of an engine mount and a suspension. However, this method just uses a parallel model of general spring and damping elements. In an actual vehicle, the portion causing the above-explained coupled vibration has non-linear characteristics such as hysteresis characteristics caused by various factors, e.g., physical properties of suspension components, or three-dimensional shape factors related to a mounting. In contrast, it is difficult for a linear model used in the method disclosed in JP-A-2011-089474, etc. to simulate the non-linear characteristics such as the hysteresis characteristics as explained above. Therefore, in related art, there is an issue that it is especially difficult to accurately identify important dynamic characteristics related to vibration suppression performance.